# Android Debugging Instructions

Chrome on Android has java and c/c++ code. Each "side" have its own set of tools
for debugging. Here's some tips.

[TOC]

## Setting up command line flags

Various commands below requires setting up command line flags.

```shell
# Content shell
build/android/adb_content_shell_command_line --flags --to-pass
# Chromium test shell
build/android/adb_chrome_shell_command_line --flags --to-pass
```

## Launching the app

You can launch the app by using one of the wrappers. You can pass URLs directly
too.

```shell
# Content shell
build/android/adb_run_content_shell 'data:text/html;utf-8,<html>Hello World!</html>'
# Chromium test shell
build/android/adb_run_chrome_shell 'data:text/html;utf-8,<html>Hello World!</html>'
```

## Log output

[Chromium logging from LOG(INFO)](https://chromium.googlesource.com/chromium/src/+/master/docs/android_logging.md)
etc., is directed to the Android logcat logging facility. You can filter the
messages, e.g. view chromium verbose logging, everything else at warning level
with:

```shell
adb logcat chromium:V cr.SomeComponent:V *:W
```

### Warnings for Blink developers

*   **Do not use fprintf or printf debugging!** This does not
    redirect to logcat.

*   Redirecting stdio to logcat, as documented
    [here](https://developer.android.com/studio/command-line/logcat.html#viewingStd),
    has a bad side-effect that it breaks `adb_install.py`. See
    [here for details](http://stackoverflow.com/questions/28539676/android-adb-fails-to-install-apk-to-nexus-5-on-windows-8-1).

## Take a screenshot

While your phone is plugged into USB, use the `screenshot.py` tool in
`build/android`. `envsetup.sh` should have put it in your path.

```shell
build/android/screenshot.py /tmp/screenshot.png
```

## Inspecting the view hierarchy

You can use either
[hierarchy viewer](https://developer.android.com/studio/profile/hierarchy-viewer-setup.html)
or [monitor](https://developer.android.com/studio/profile/monitor.html) to see
the Android view hierarchy and see the layout and drawing properties associated
with it.

While your phone is plugged into USB, you can inspect the Android view hierarchy
using the following command:

```shell
ANDROID_HVPROTO=ddm monitor
```

Setting `ANDROID_HVPROTO` allows you to inspect debuggable apps on non-rooted
devices.  When building a local version of Chromium, the build tools
automatically add `android:debuggable=true` to the `AndroidManifest.xml`, which
will allow you to inspect them on rooted devices.

Want to add some additional information to your Views? You can do that by
adding the
[@ViewDebug.ExportedProperty](https://developer.android.com/reference/android/view/ViewDebug.ExportedProperty.html)
annotation.

Example:

```java
@ViewDebug.ExportedProperty(category="chrome")
private int mSuperNiftyDrawingProperty;
```

## Debugging Java

*   In Eclipse, make a debug configuration of type "Remote Java Application".
    Choose a "Name" and set "Port" to `8700`.

*   Make sure Eclipse Preferences > Run/Debug > Launching > "Build (if required)
    before launching" is unchecked.

*   Run Android Device Monitor:

    ```shell
    third_party/android_tools/sdk/tools/monitor
    ```

*   Now select the process you want to debug in Device Monitor (the port column
    should now mention 8700 or xxxx/8700).

*   Run your debug configuration, and switch to the Debug perspective.

## Waiting for Java Debugger on Early Startup

*   To debug early startup, pass `--wait-for-java-debugger` as a command line
    flag.

## Debugging C/C++

Under `build/android`, there are a few scripts:

```shell
# Convenient wrappers
build/android/adb_gdb_content_shell
build/android/adb_gdb_chrome_shell

# Underlying script, try --help for comprehensive list of options
build/android/adb_gdb
```

By default, these wrappers will attach to the browser process.

You can also attach to the renderer process by using `--sandboxed`. (You might
need to be root on the phone for that. Run `adb root` if needed)

## Waiting for Debugger on Early Startup

Set the target command line flag with `--wait-for-debugger`.

Launch the debugger using one of the `adb_gdb` scripts from above.

Type `info threads` and look for a line like:

```
11 Thread 2564  clock_gettime () at bionic/libc/arch-arm/syscalls/clock_gettime.S:11
```

or perhaps:

```
1  Thread 10870      0x40127050 in nanosleep () from /tmp/user-adb-gdb-libs/system/lib/libc.so
```

We need to jump out of its sleep routine:

```
(gdb) thread 11
(gdb) up
(gdb) up
(gdb) return
Make base::debug::BreakDebugger() return now? (y or n) y
(gdb) continue
```

## Symbolizing Crash Stacks and Tombstones (C++)

If a crash has generated a tombstone in your device, use:

```shell
build/android/tombstones.py --output-directory out/Default
```

If you have a stack trace (from `adb logcat`) that needs to be symbolized, copy
it into a text file and symbolize with the following command (run from
`${CHROME_SRC}`):

```shell
third_party/android_platform/development/scripts/stack --output-directory out/Default [tombstone file | dump file]
```

`stack` can also take its input from `stdin`:

```shell
adb logcat -d | third_party/android_platform/development/scripts/stack --output-directory out/Default
```

Example:

```shell
third_party/android_platform/development/scripts/stack --output-directory out/Default ~/crashlogs/tombstone_07-build231.txt
```

## Deobfuscating Stack Traces (Java)

You will need the ProGuard mapping file that was generated when the application
that crashed was built. When building locally, these are found in:

```shell
out/Default/apks/ChromePublic.apk.mapping
out/Default/apks/Chrome.apk.mapping
```

To deobfuscate a stack trace from a file, run

```shell
build/android/stacktrace/java_deobfuscate.py PROGUARD_MAPPING_FILE.mapping --stacktrace STACKTRACE_FILE
```

Deobfuscation also works from `stdin`:

```shell
adb logcat -d | build/android/stacktrace/java_deobfuscate.py PROGUARD_MAPPING_FILE.mapping
```

## Get WebKit code to output to the adb log

In your build environment:

```shell
adb root
adb shell stop
adb shell setprop log.redirect-stdio true
adb shell start
```

In the source itself, use `fprintf(stderr, "message");` whenever you need to
output a message.

## Debug unit tests with GDB

To run unit tests use the following command:

```shell
out/Debug/bin/run_test_name -f <test_filter_if_any> --test-arguments=--wait-for-debugger -t 6000
```

That command will cause the test process to wait until a debugger is attached.

To attach a debugger:

```shell
build/android/adb_gdb --output-directory=out/Default --package-name=org.chromium.native_test
```

After attaching gdb to the process you can use it normally. For example:

```
(gdb) break main
Breakpoint 1 at 0x9750793c: main. (2 locations)
(gdb) continue
```
